This application claims priority from application serial number 100 62 973.3 which was filed in Germany on Dec. 16, 2000.
The present invention relates to chain joints for high strength linked chains.
DE 199 14 014 A1 discloses a chain joint in which the two joint parts can be brought into engagement with one another under displacement in the longitudinal direction. For this purpose, the one joint part comprises a peg and the other joint part a receiver. This chain joint is locked by a center piece employed as a joining element which is in contact on a support face of a projection associated with each longitudinal side bar and projecting into the opening encompassed by the joint parts. This joining element developed as a center piece comprises a fitting plug which carries three retaining rings disposed in grooves. The fitting plug comprises a cylindrical shell such that the support faces, associated with the two longitudinal side bars, are correspondingly developed complementarily in the form of a trench. After the two joint parts have been brought form-fittingly into engagement, the locking of the joint parts takes place by the driving of the fitting plug into the volume encompassed by the support faces. A relative movement of the two joint parts in the longitudinal direction toward one another is prevented by the introduction of the fitting plug. Into each support face is introduced a groove which, with the specified positioning of the fitting plug, a retaining ring engages such that a user can perceive when the fitting plug is in its specified locking position between the support faces.
However, in the case of the subject matter of this chain joint through the center piece not only a locking of the chain joint is provided but the bracing of the two longitudinal side bars of the joint parts also takes place in the center region against one another such as is also known from the German Utility Model 298 11 332 U1. The center bar described in this document is formed in the case of the subject matter of DE 199 14 014 A1 by the projections carrying the support faces and the center piece. The center bar serves as a support between the two longitudinal side bars in order to counteract the constriction of the longitudinal side bars under tensile loading of the chain joint.
By providing such a center bar developed in several parts such as in the subject matter of DE 199 14 014 A1, however, operation of the center piece comprised of the fitting plug and the retaining rings employed as fitting elements is considered disadvantageous. This is because the chain links suspended in a joint part hardly have enough space for the chain links adjoining the chain joint to be moved in the openings of the chain joint to open or close the chain joint by displacing the two joint parts in the longitudinal direction relative to one another. Moreover, the operation during the driving-in or driving-out of the center piece serving as locking is not always free of problems due to the fitting plug, which, in the subject matter of DE 199 14 014 A1, is intentionally kept as small as feasible.
Building on this discussed prior art, the present invention therefore addresses the problem of further developing a chain joint or a center piece described in the introduction such that the listed disadvantages entailed in prior art are avoided.
This problem is solved according to the invention, for one, with a chain joint and, for another, with a center piece, in each case thereby that as the fitting element serves a fitting sleeve into which the fitting plug can be set and in which the fitting plug is at least largely enclosed.
The chain joint of the present invention and, correspondingly also in the claimed center piece, is formed from a fitting sleeve, which functions as a fitting element with resilient material properties, and fitting plug, which can be set into the fitting sleeve. After the fitting plug has been set into the fitting sleeve it is at least predominantly enclosed in the fitting sleeve. Setting the center piece in the present invention can take place in two steps. First the fitting sleeve is disposed in its specified position between the two longitudinal side bars of the joint parts. Then the fitting plug is set into the fitting sleeve, using hammer blows or similar methods.
The fitting sleeve of the present invention compared to a retaining ring from prior art is considerably larger and therefore much simpler to handle and easier to get into place. In rough operation below ground and similar locations the ease of setting the fitting sleeve can be very advantageous. The fitting sleeve can moreover be manufactured of a synthetic material such that it can be fabricated in a cost-effective manner, for example by way of an injection molding process. The fitting plug to be set into the fitting sleeve accordingly does not have to have grooves but is appropriately only chamfered at its two ends. Thus the difficult step necessary in the prior art of introducing the grooves into the fitting plug receiving the retaining rings is thus eliminated. The fitting sleeve also permits the pre-assembling of the two joint parts with respect to one another. This allows a preliminary security function in that the center piece can be employed as a preliminary locking element. Only when the chain joint is in fact to be closed, the fitting plug is driven into the fitting sleeve in order to be subsequently held clamped between the two longitudinal side bars, separated from them by the fitting sleeve.
Therefore the center, in principle, can also be employed in such chain joints or also in individual chain links if only a mutual bracing of the longitudinal side bars is desired. For this purpose it fundamentally does not require additional complex and expensive measures. When support faces are provided on the longitudinal side bars, it is sufficient if these have each recesses of low depth in order to define the set-in position of the sleeve. It can also be provided to form projections on the two longitudinal side bars opposing one another, which form support faces on the sides facing one another, between which the fitting sleeve and the fitting plug are disposed as the center piece.
It is also possible in the present invention for the fitting plug, as well as the fitting sleeve, to have a cross sectional other than the conventional circular cross sectional area, for example an oval or rectangular form. In the case of such a form the width of the center bar also formed by this center piece is relatively narrow even at a relatively large distance of the longitudinal side bars of the joint parts with respect to one another. This means that more space is available for moving suspended chain links in order to be able to open and close such chain joints without any of the problems seen in those joint parts which must be displaced in the longitudinal direction relative to one another for opening and closing the chain joint.
In the preferred embodiment beadings indicate the set-in position of the fitting plug within the fitting sleeve. These beadings are located at each end of the fitting sleeve and project inward to enclose the fitting plug at each end. It is useful to design the fitting sleeve such that the fitting plug can only be set into the fitting sleeve from one side by having one of the beadings project in much further. This allows the larger beading to function as a stop for limiting the driving-in movement of the fitting plug.
The fitting sleeve can also be provided with outwardly projecting collars, or flanges, which fit into support shoulders on the support faces of the longitudinal side bars. These collars both hold the fitting sleeve in place between the support faces and prevent the unintentional ejection of the sleeve during the driving-in of the fitting plug.
The present invention is a chain joint for a high-strength link chain comprising two joint parts form-fittingly connected with one another and a center piece braced on the two opposing longitudinal side bars of the joint parts and detachably disposed with respect to the joint parts. The center piece comprises a fitting plug and at least one fitting element indicating, based on resilient material properties, the specified set-in position of the fitting plug. Another aspect of the present invention is a center piece for a chain joint of a high-strength steel link chain with a fitting plug and at least one fitting element indicating the set-in position of the fitting plug based on resilient material properties.
Other aspects of this invention will appear from the following description and appended claims, reference being made to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.